In clinical practice, recombinant antibody has been used to treat a variety of diseases, including cancer and autoimmune diseases. Currently, genetically engineered antibody is generally produced in vitro and then injected into the body for treatment. However, this approach has many disadvantages, such as: (1) high cost of the production, packaging, transportation, etc; (2) low purity of protein antibody medicines, side-effects caused by contaminant, potential safety hazard; (3) antibody should be injected repeatedly due to its short half-life period. Sometimes, we need to maintain the effective concentration in vivo via a micropump administration, making it more difficult to apply antibody in clinical practice.
One effective way to avoid the problems caused by a direct injection of protein antibody medicines is to transfect human target cells with therapeutic genes, which is known as gene therapy. In the gene therapy, it is very important to transfer the target genes effectively and safely to host cells for expression via an effective vector. The vectors used in clinical practice mainly comprise recombinant adenoviral vectors, retroviral vectors and plasmid vectors. The viral vectors have high transfection rate, however, it is high in production cost, and its risk of insertion mutagenesis and immunogenicity will bring the risk of carcinogenesis and fatal immune response in patients. Traditional virus vector plasmid vectors are safer than viral vectors, but lower in transfection rate. Further, exogenous genes can only be transiently expressed. If you want a stable and lasting expression of exogenous genes, the vectors must be integrated into the host cell chromosome suffering from the possibility of insertion mutagenesis and exogenous genes silencing. In addition, traditional plasmid vectors contain some hidden signals such as bacterial replication sequences, resistance genes and unmethylated CpG gene sequences, which are necessary in plasmid replications and may cause severe biological safety issues in gene therapy.